Topic: C128 $d030 Test Bit vs. color pallette

[XmikeX]

Going over this http://sites.google.com/site/h2obsession/CBM/C128/Interlace (i think it's hydrophilic's site?), I noticed this -> "Update:AmiDog reports an even more fantastic color distortion on PAL systems with the appropriate (wrong for proper interlace) settings. It seems a good PAL hack could produce a new color pallette for the VIC-IIe! "

Is this the same technique discovered at least as far back as 2001 ( @ Risen From Oblivion  (VIC parts) comes to mind, as seen here - http://noname.c64.org/csdb/release/?id=2942 ) ?

The comments seen at the csdb link seem to suggest it is the same material :

"Submitted by DeeKay on 26 November 2006
Amidog: Frankly, we don't quite know ourselves! ;-) Crossbow was experimenting with that $d030-bit that almost all of the effects in the demo are based on and he noticed the colors came out different under certain conditions, because that bit forces an early restart of the screen and seriously fucks with the video signal. It does not work on every monitor we've noticed, some (Philips?) show the original colors!"

"Submitted by Graham on 3 December 2006
The new colors work because of the PAL color encoding: The color carrier consists of U (blue-yellow color distance) and V (red-cyan color distance) which are simply added together, so C = U + V. Now, because a decoder needs to seperate U and V again, the inventors of PAL used a simple trick: They inverted the sign of V every 2nd rasterline, so you always have C = U + V followed by C = U - V. This way you can simply take the color carrier of the previous rasterline and add or subtract the current rasterline with it. If you add both carriers you get back U, and if you subtract you get V or -V. Now, if you skip an odd number of rasterlines, you get -V where normally would be +V and you get +V where normally would be -V. -> The red-cyan color distance gets inverted."

..and so forth...

Any modern updates regarding this trickery?

XmX

EDIT: I'm sure the VDC parts of Risen From Oblivion are well known here but just in case : http://noname.c64.org/csdb/release/?id=44983

[Hydrophilic]

Wow, talk about timing!  I just got an email from DeeKay (an author of the infamous Risen to Oblivion).  Anyway, it turns out that several (I think 6) new colors are available through $d030 trickery, but it only works on PAL systems.
I have an NTSC machine so I can't be sure.
 
An old trick for PAL is to use two colors on adjacent rasters which have the same intensity... and then a PAL monitor will "blend" the two colors.
 
The new trick (possible with C128) is to "cut" 3 rasters (or any odd number of raster) with $d030 bit 1.  Which will effectively convert PAL's YUV into YVU.  In other words the color signals get scrambled and you get new colors.  Again, I don't have any details because I have NTSC.

[XmikeX]

Wow, talk about timing!  I just got an email from DeeKay (an author of the infamous Risen to Oblivion).  Anyway, it turns out that several (I think 6) new colors are available through $d030 trickery, but it only works on PAL systems.

Well, the timing is just a little too precise.

I pointed Deekay, Graham, etc, to your site, while I was writing the text here. =)

If you or anyone else is interested, these guys and other legendary-european demo freaks tend to hang around IRC (Internet Relay Chat) .. on the IRCNET network ( ircnet.eversible.com is one of the open servers ),  join channel #c-64  ..

( Pertinent to hydrophilic -- Graham, the guy behind the VDC part of RFO and utilities like Warpcopy, is especially interested in coding z80 on the 128....if a "simple" 4 MHz z80 fix happens. )

XmX